Patent Literature 1 discloses a light sensor which is one of conventional light sensors and which includes a first light receiving portion for detecting light ahead of a vehicle, a second light receiving portion for detecting light above the vehicle, and a control circuit portion for determining whether a light in the vehicle is turned on or off on the basis of signals from the light receiving portions.
With the structure of such a light sensor, timing when the light intensity detected by the first light receiving portion is lowered to below a threshold value is different from timing when the light intensity detected by the second light receiving portion is lowered to below a threshold value. Accordingly, the light sensor does not turn on the light in the vehicle under a constructed structure such as a bridge girder.
However, with the aforementioned conventional technique, the light sensor includes the control circuit portion adapted to determine whether the light is turned on or off, as well as to detect light. This induces the problem of complicacy of the structure of the light sensor and, furthermore, induces the problem of an increase of the size of the light sensor. There has been a need for reduction of the sizes of light sensors, because such a light sensor is mounted on a front glass, a dash board, or the like.